Study on oxidation behaviors of Zr–Sn–Nb alloy in water steam at 1250 °C

To investigate the effect of different oxidation times on the oxidation behavior of Zr–Sn–Nb alloy in a high-temperature steam environment at 1250 °C, steam oxidation tests were conducted on the Zr–Sn–Nb alloy at 1250 °C for durations ranging from 100 to 5000 s. Microstructural and elemental composition analyses of the Zr–Sn–Nb alloy were carried out using scanning electron microscopy, energy-dispersive x-ray spectroscopy, and optical microscopy. The results showed that in the initial stages of oxidation (0–1000 s), the weight gain per unit area followed a parabolic trend. After 2500 s of oxidation, the weight gain rate significantly increased. In the later stages of oxidation (after 4000 s), the weight gain curve transitioned from a parabolic shape to a linear law. With increasing oxidation time, the thickness of the oxide layer gradually increased. In the early stages (0–2500 s), the growth rate of the oxide layer thickness was relatively slow, but the appearance of micro-pores and cracks was observed. However, after 2500 s, the steam oxidation rate of the Zr–Sn–Nb alloy significantly accelerated, leading to fracture and failure of the alloy specimens. The change in oxide layer thickness over time followed a parabolic law before 2500 s and a linear law after 2500 s. The growth curve of the α-Zr(O) layer within 5000 s also followed a parabolic law.